Geochemistry of Crystalline Rocks from the East of the Upper East Region of Ghana

Abstract

Abstract: Selected rock samples were collected from outcrops from the eastern part of the Upper East Region with the aim of determining their chemical composition and classification. Samples were obtained from granitoids and the Birrimian formation located in Bongo, Talensi-Nabdam, Bawku West and Garu-Tempane Districts. Rocks were identified mineralogically using hand lenses. The composition of the samples was determined using X-Ray Fluorescence (XRF) after which several quantitative and qualitative techniques were employed to analyse the data. Some of these techniques included physical examination, Chemical Alteration Index (CIA), scatter plots, discrimination diagrams and Aluminium Saturation Index (ASI). The mineralogical analysis showed that the rocks generally contained K-feldspar, plagioclase, muscovite, hornblende, quartz and biotite as major minerals. Physical examination revealed that samples had undergone some alteration that was not evident at the time of sampling and this was confirmed by calculations using the Chemical Index of Alteration (CIA). The CIA values of the fresh rocks ranged from 70 to 125 suggesting that the samples had undergone intensive alteration. Scatter plots and discrimination diagrams suggested that the samples were not of basaltic origin but were thoeleiitic in character. The Aluminium Saturation Index (ASI) revealed that most samples were metaluminus and that the majority of samples were sub-alkaline and therefore basic in character